Yams are among humans’ oldest foods [34] and have been recorded in archaeological sites since the Pleistocene [35]. Archaeological remains of Dioscorea have been recovered from sites in Brazil dating back to the early Holocene [70], a period that in Babitonga Bay is related to the presence of hunter-gatherers from the Umbu tradition dating from 11,000 to 8000 years cal BP [71, 72] (Fig. 5).

Timeline with recorded Dioscorea species in the study area and precolonial and colonial human groups

The history between yams and people in Babitonga Bay began thousands of years ago, and even today, we find plants producing these tubers associated with places built at different times by different people and their cultures. The oldest record of Dioscorea consumption in Babitonga Bay is among the Sambaquianos in 4030 ± 40 years BP [31]. Another ancient record of yam consumption among Sambaquianos was found in the south of Santa Catarina [33]. In southeastern Brazil, charred archaeological fragments of Dioscorea tubers were found in shellmounds dating back to approximately six thousand years BP [23].

The shellmounds we researched date back to between 5200 and 2900 years BP (Table 1). Dating indicates that the construction of sambaquis in Babitonga Bay occurred between 6 thousand and 1000 years BP [21, 73]. Radiocarbon dating indicates the presence of indigenous people Jê in Babitonga Bay from 1500 years BP [74]. The Guarani left their records in archaeological sites in Babitonga Bay from 400 years BP [74] (Fig. 5), a period in which European colonizers were already present in the region [64, 75, 76]. There are archaeological and ethnoarchaeological records that the Jê and Guarani indigenous groups also consumed Dioscorea in other regions of the state of Santa Catarina [62, 63, 77]. The oldest record of European contact in Babitonga Bay is by Binot Palmier de Goneville in 1504 [64]. According to the account of this French explorer, he found the Guarani, then called Carijós, with dozens of villages where they cultivated cassava (Manihot esculenta Crantz) and other roots and tubers, probably sweet potato, Ipomoea batatas (L) Lam., and yams (Dioscorea spp).

We recorded species of Dioscorea associated with sambaquis and swiddens in the Babitonga Bay region that maintain different relationships with people (Figs. 5, 6). Associated with the shellmounds are wild species of Dioscorea—D. chondrocarpa, D. dodecaneura, D. laxiflora, D. olfersiana and D. scabra—and the exotic D. cayennensis. In the swiddens, domesticated yams, D. alata (Asian), D. cayennensis (African), D. bulbifera (Asian and African) and D. trifida (Amazonian) [44, 48, 58, 59].

Dioscorea species in shellmounds and swiddens. A Shellmound Cubatão I—B; B Dioscorea dodecaneura over Cubatão I—A; C D. cayennensis over Cubatão I—B; D D. trifida in swiddens on Cubatão Grande Road; E D. trifida in swiddens on João Fleith Road

Dioscorea trifida and D. dodecaneura are among the yam species cultivated by Guarani [62, 77]. These and other Dioscorea species are associated with the Guarani plant pack, a set of plants and their propagules (seeds, roots, tubers and others) carried by them in their expansion to new territories, including southern Brazil, 2000 years BP [62]. Dioscorea trifida is from the Amazon rainforest [78] and was domesticated by indigenous people before the European invasion. Genetic studies indicate that accessions of D. trifida from Babitonga Bay are linked to the Amazon and that their origin is related to Guarani expansion [59] (Nascimento 2013). In the Amazon region, according to Clement [78], D. dodecaneura is considered semidomesticated and a food source for indigenous peoples before European invasion, in addition to domesticated D. trifida.

Dioscorea chondrocarpa, D. dodecaneura, D. laxiflora, D. olfersiana and D. trifida began to be cultivated by farmers in Brazil through contact with indigenous peoples [46, 47]. By 1550, the African yam (probably D. cayennensis) was already cultivated in southeastern Brazil by colonizers and their slaves, but the indigenous people preferred the native yams that they already cultivated and because they had better flavour [79]. This may also have been the scenario in Babitonga Bay.

The exotic species D. cayennensis, D. alata and D. bulbifera arrived in Brazil with colonizers from the sixteenth century onwards [43]. In Babitonga Bay, the historical record of cultivation of D. alata [65] and D. bulbifera [50] was initiated by Luso-Brazilians who arrived in the region in the seventeenth century [49, 76, 80]. Currently, they are cultivated by descendants of the Germanic colonizers who arrived in the region in the nineteenth century [44, 48, 58, 59] (Fig. 5).

The lack of historical records on the consumption of yams native to the region by colonizers does not mean that it did not occur but may be related to the type of use that Luso-Brazilian and Germanic colonizers made of the forest in the nineteenth century. According to Saint Hilaire [65] and Rodowicz-Oświęcimsky [50], in the region, food came from swiddens with domesticated species, such as the abovementioned species, and forests were intensively cut down to build villages. At the same time, some shellmounds were dismantled to extract the shells, which lasted until the mid-twentieth century [52]. These two actions resulted in the loss of vegetation and native Dioscorea species and the introduction of exotic species, as observed in some shellmounds (Table 3, 4 and Fig. 2).

Despite the strong association of native species of Dioscorea with shellmounds and diverse uses, there is no evidence or current records in the literature that the descendants of the colonizers have appropriated these species. Currently, descendants cultivate domesticated yams, and forest areas are replaced by different crops. Wild yam is a plant with great potential for use and is apparently not known. An important aspect to be considered in possible future uses of the vegetation associated with shellmounds is that they are archaeological sites protected by law, and interventions are prohibited without prior authorization by the National Institute of National Historical and Artistic Heritage (IPHAN, Brazil).

Considering that the exotic African and Asian species of yam arrived in Brazil only after colonization in the sixteenth century, we can infer that the Sambaquianos, Jê and Guarani consumed the native species of Dioscorea, and among these, the native species that currently occur are associated with shellmounds and D. trifida is associated with swiddens.

The Babitonga Bay landscape is home to approximately 170 sambaquis [73] that are integrated into the Restinga forests and mangroves. Among the sambaquis researched, the exception is the Rua Guaíra, which was built on the slope of a small hill and is currently associated with the Dense Ombrophilous Forest. However, although they are currently integrated into the abovementioned ecosystems, they contain plant species from other regions of Brazil and even other countries. For example, in some shellmounds, we recorded exotic food plants related to European colonization (Table 4). In the case of Persea americana (avocado) and Psidium guajava (guava), which are not native to the region, they were probably already cultivated in Brazil before colonization [81, 82]. In the vegetation on and around the sambaquis, we recorded six species of Dioscorea, five native and the exotic D. cayennensis, African yam. The occurrence of plants of different origins indicates human influence at different times that have moulded the current landscape.

The expressive presence of sambaquis in the current landscape refers to an intense interaction between their builders and the environment. Archaeobotanical studies in shellmounds indicate that Sambaquianos mainly uses Restinga plants [23], including in Babitonga Bay [19]. However, Archaeobotany is a recent area of research in Brazil [83], and this is reflected in the small collection of archaeological food plant remains identified in shellmounds. Most of the archaeobotanical remains identified in sambaquis are from tree species from charcoal [19, 23, 84]. The first use mentioned is as fuel, but it is clear that many of the identified species produce edible fruits. The Myrtaceae family, which is very diverse in Restinga and well represented in archaeological remains [23], produces fruits that are highly appreciated by people. Examples are species of the genera Psidium and Eugenia [23], which we recorded to be associated with the sambaquis studied as Psidium cattleyanum (araçá) and Eugenia astringens Cambess (jabuticaba-da-praia). We recorded other plant species from Restinga associated with shellmounds, previously identified archaeological remains in Babitonga Bay. Trees such as Andira fraxinifolia and palm Syagrus romanzoffiana were identified by Melo Junior et al. [19] and Oliveira and Melo Junior [84]. Of the remains identified as Araceae by Wesolowski et al. [31] and Philodendron [85], we recorded Monstera adansoni and Philodendron appendiculatum in the current vegetation. Food plants such as Dioscorea spp. also identified by Wesolowski et al. [31] we registered in shellmounds D. chondrocarpa, D. dodecaneura, D. laxiflora and D. olfersiana, and medicinal plants D. scabra. All of these plants and countless others, with different uses for people, are in wild conditions and do not depend on human action to reproduce, persist and perpetuate in the environment.

Direct identification of plant consumption among Sambaquianos was carried out through the extraction of remains in dental calculi by Wesolowski [30] and Boyadjian [32] and by stable isotopes Pezo-Lanfranco et al. [86] and Toso et al. [87]. Among the remains, starch granules of Dioscorea sp. were identified, others suggestive and similar to Ipomoea batatas (sweet potato), Zea mays (corn) and Araucaria angustifolia [31, 33]. According to these authors, other remains, including starch granules and phytoliths, were identified as Marantaceae, Araceae and Poaceae.

Given the archaeobotanical research cited above, there is no doubt that the Sambaquianos used and consumed plants and that the consumption of carbohydrates was significant, as noted by Wesolowski [30] and Pezo-Lanfranco et al. [86]. Based on this reduced archaeobotanical data set of evidence for plant consumption, Pezo-Lafranco et al. [86] in their research and in review articles Scheel-Ybert and Boyadjian [29] and Scheel-Ybert et al. [88] suggest a mixed economy among Sambaquianos with the cultivation of domesticated plants.

Although there has been a record of plant cultivation in Brazil since 12 thousand years BP [82], it is still premature to confirm horticulture and the cultivation of domesticated plants among shellmound builders. Even with the spread of horticulture and agriculture, indigenous groups choose not to do so. In the Neotropics, there are several systems for obtaining food plants that are independent of cultivation and domestication [82]. In the lowlands of South America, of the 6261 plant species used, only 0.7% are completely domesticated, and gathering represents 98.6% of the way to obtain useful plants, among which 53% are trees [82]. Edible tubers of Dioscorea species can be collected and managed in the forest and cultivated [36, 40, 44, 46, 47, 89]. For example, the indigenous Nukak people in the Amazon form wild orchards where they promote some species over others, thus increasing the productivity of the forest [90].

There are wild species of Dioscorea [43, 46, 47], Ipomoea [91, 92] and Poaceae [93] that are used in food and that could simply be gathered and managed. It is not always easy to distinguish between remains, such as starch grains and phytoliths, from wild and domesticated plants [93, 94].

Currently, native species of Dioscorea recorded in shellmounds and surrounding vegetation perform sexual reproduction and do not depend on human action for their perpetuation in the environment. However, this does not rule out human influence in the past. Interactions between people and forests have occurred for thousands of years and can be perceived through patches of useful plants near archaeological sites [4,5,6,7,8,9,10,11,